let's be realist: is it your daily commuter, or is it your weekend fun car?
Until last week, it was my daily commuter (60 mile round trip). The only reason it isn't now is that I just started a new job that's close enough to commute by bicycle. The thing may be 25 years old, but it's only got 85K miles on it and is in great condition (except for the fact that it has a tape deck, pop-up headlights and only one airbag, you'd think it was brand new).
I admit, it's also my fun car since I use it for autocross, too.
FYI, before I bought the Miata, I'd been doing the same commute for years in my 1996 pickup truck with 215K miles on the odometer. My wife is now using it for her 50 mile round trip daily commute. That's actually more impressive, since the truck is much more worn-out than the Miata even though it's newer.
My newest car, a 1998 VW, is currently partially-disassembled because the transmission broke. Clearly, age isn't everything.
Is it also a "pre-electronics" car? Do you expect it to last as long as you?
It's got electronic fuel injection, but it's pre-ODBII. I don't expect any individual part on the car to last forever, but certainly I expect it to be repairable (or even upgradable) indefinitely as long as the chassis doesn't rust out.